Allocyclinones, hyperchlorinated angucyclinones from Actinoallomurus.

A screening program on a limited number of strains belonging to the Actinoallomurus genus yielded a series of new angucyclinones. NMR and MS analyses established that these compounds are characterized by an unusual lactone ring and present up to four halogens per molecule, with one congener representing the first natural product containing a trichloromethyl substitution on an aromatic system. Remarkably, this family of metabolites seems to be produced by phylogenetically distinct Actinoallomurus isolates. Because of the unique structural features and wide distribution among Actinoallomurus, we have designated these angucyclinones as allocyclinones. Allocyclinones possess interesting activity against different Gram-positive bacteria, including antibiotic-resistant strains, with antibacterial potency increasing with the number of chlorine substituents. The tetrachlorinated compound is the most abundant congener in the allocyclinone complex.